The invention relates to a slide bearing of a centrifugal pump that is lubricated by the pumped medium and comprises a stationary part disposed in the housing of the centrifugal pump and a rotatable part disposed on the shaft of the centrifugal pump and interacting with the stationary part to form a sliding pair. One part of this sliding pair is made of a composite material, particularly of carbon fibers or silicon carbide (SiC) fibers with a matrix of polyetheretherketone (PEEK), carbon, or carbon and silicon carbide, while the other part has a sliding surface that is made of a hard metal material and is supported by a supporting material.
Tribological investigations have shown that the loading capacity of self-paired composite materials used in slide bearings is limited. However, if a sliding pair has hard, smooth-polished counter-rotating elements, the pair has excellent properties for use in bearings lubricated by the medium. Among other things, such a pair is highly wear resistant. This is due to the fact that the very hard counter-rotating elements are wear resistant even under high tribological loading in the mixed friction range, in part even with simultaneous solid loading. As a consequence, there is no abrasive wear on the hard counter-rotating partner elements. Nor can the products of abrasive wear destroy the softer counter-rotating partner element. Wear-related widening of the clearance is minimized.
One known measure to realize a slide bearing with the described properties is to apply a hard coating with a strong bond to the counter-rotating partner element of the bearing part that is made of a composite material. This type of hard coating based on chromium carbide, aluminum oxide, titanium oxide, or metal layers has proven successful when used with non-corrosive, chemically neutral, chloride-free media. However, the resistance of such slide bearings against chloride-containing and/or corrosive media is limited because of the risk of subcorrosion underneath the coatings. This type of corrosion causes the coating to chip or spall and thereby destroys the slide bearing, which in turn can have far reaching consequences for a centrifugal pump that is equipped with such a slide bearing.